While the Central Valley has seen more than a dozen deaths from the H1N1 strain of the flu virus the Fresno County Health Department is reporting an increase in pertussis cases, or whooping cough.

The Fresno County Department of Health is seeing a spike in pertussis with 17 cases reported since November. School officials at University High School in Fresno say they were shocked to learn two of their students tested positive for the whooping cough.

"The health department has notified us that they are at home, and that they are being monitored by them," Dean of Students Jeffie Hickman said.

According to California state law all children 7th grade should receive a vaccine booster known as the Tdap, but health department officials say the vaccines are not 100 percent guaranteed.

"We hate to see cases in high school because we know most of them have been vaccinated, but we do know that the vaccine is not a hundred percent perfect, but it is still the best tool we have to protect us against this disease," said David Luchini with the Department of Health.

Pediatrician Laura Schilling said her office has seen three cases of whooping cough in the last two weeks. Early symptoms may include a persistent cough, runny nose and a low grade fever. Schilling said for every case that is diagnosed there are about 200 that are not.

"In order to truly diagnose whooping cough you have to do a nasal swab which is not done with every patient that presents with the symptoms of whopping cough because it presents itself looking much like any other cold," Schilling said.

Schilling says there isn't a clear indication of how long the vaccine lasts, so if you are around children or pregnant you should talk to your doctor about getting a vaccine booster.

"At this point in time the recommendation is that you get a booster about every ten years. We don't know for sure one hundred percent how long the vaccine is going to last," Schilling said.

Officials at University High are making sure to keep classrooms extra clean to avoid spreading germs. Health officials are advising if you have an ongoing cough get tested.